1. Field of the Invention
The present invention relates generally to machinery for processing foods and, more particularly, to a sheeting head or xe2x80x9csheeterxe2x80x9d for processing dough into relatively thin sheets out of which corn tortillas, tortilla chips, sheeted corn chips, sheeted potato chips, and similar food products are cut and to an improved system for handing the rotary cutter which cuts the dough sheet.
2. Description of Related Art
Maize (corn) is the chief cereal grain of the Americas, but dried maize cannot be readily steamed into a palatable staple like rice. Consequently, the native American peoples developed a technique in which they cooked dried maize with calcium carbonate or other alkali and then ground the resulting cooked kernels to produce a sticky dough known as masa.
Traditionally masa dough was shaped by hand and baked on a stone griddle to make tortillas. The popularity of tortillas and other comestibles made from masa has continued to increase. Today special machines called sheeting heads form the masa into relatively thin sheets from which tortillas and other food products such as chips or tortillas are cut. As shown in cross-section in FIG. 1a, a typical sheeting head comprises a pair of parallel counterrotating rollers, a front-roller 12 and a rear roller 14, rotating on horizontal axes between a spaced pair of side plates 17. Masa dough 16 is loaded into the sheeting head, where it is drawn between the rollers and formed into a thin sheet 18 in a pinch point or extrusion zone.
The dough is sticky and tends to cling to both rollers. However, differential roller motion or a physical stripping device like a wire or a xe2x80x9cdoctor bladexe2x80x9d transfers the dough sheet to the front roller 12. As the rollers rotate, the sheet of dough is carried away from the extrusion zone by the front roller 12.
A rotary cutter, 24 sometimes called a cutter roller, counterrotates on a shaft 25 and is in contact with the front roller 12. The surface of the rotary cutter 24 bears a series of raised ridges that define the shapes of the tortillas, chips, or other products to be cut from the masa dough sheet 18. When the rotary cutter 24 rotates into contact with the dough sheet 18, carried by the front roller 12, the ridges cut the dough sheet 18 into pieces 26. The cut dough pieces 26 still stick to the front roller 12, but as the cut dough pieces 26 are moved along by the rotation of the front roller 12, they come into contact with a stripper wire 22 which scrapes the dough pieces from the front roller 12.
The dough pieces 26 fall onto a moving conveyor belt 28 which carries them into an oven or fryer for final cooking. In some sheeting heads an ingenious system of grooves and bands on the front roller retains edge remnants of the dough sheet on the roller. Thus, only the desired cut dough pieces 26 are removed by the stripper wire 22. The front roller 12 carries the dough remnants or xe2x80x9creworkxe2x80x9d back into the top of the sheeting head to be added back in to the main mass of dough for recycling.
The rotary cutter 24 requires rather frequent attention. It is not unusual to replace the rotary cutter 24 during a shift either because chips or tortillas of a different size or shape are desired or because the rotary cutter 24 has become worn or damaged.
Some sheeters include a mechanism that alternately engages or disengages the rotary cutter 24 from interaction with the dough sheet 18. FIGS. 1a to 1c, for example, show an air cylinder 32 including a piston 37 attached to a pivoting lever arm 34 which terminates in a yoke 38 that carries the rotary cutter 24. When the cylinder 32 is energized as in FIG. 1a, the lever arm 34 pivots upward to bring the rotary cutter 24 into contact with the dough sheet 18. When the cylinder 32 is not energized as in FIG. 1b, the weight of the rotary cutter 24 causes the lever arm 34 and the attached rotary cutter 24 to swing away from the dough sheet 18. An advantage of this arrangement is that whenever the sheeting head power is turned off, the rotary cutter 24 is automatically moved out of contact with the dough sheet 18 into a removal position where the rotary cutter can be removed from the lever arm 34.
Nonetheless, severe removal problems still exist because, as shown in FIGS. 1a-1c, the rotary cutter 24 is inaccessibly located between the side plates 17 and beneath the front roller 12, making it difficult to reach the cutter from the back of the sheeting head or from the side. The conveyor belt 28 and other mechanisms generally make it impossible to access the rotary cutter from the front side as well. Accordingly, the side plates 17 in a conventional sheeting head are provided with access ports or lower cut outs 19, as shown, so that the rotary cutter 24 can be inserted and removed from the side.
The rotary cutter 24 is typically removed through the access port 19, as shown in FIG. 1C, by laboriously lifting it out of the yokes 38 of the pivoting lever arms 34 and then carefully guiding it through the access port 19 in one of the side plates 17. Cutter replacement is accomplished by reversing this process. In either case, it is troublesome, time-consuming, and may result in injury to the operator or damage to the rotary cutter.
There remains a considerable need, therefore, for a system that makes cutter replacement simple and avoids the need to work through the side plates and under the rollers of the sheeting head to service or replace the rotary cutter.
It is an objective of the present invention to provide a simple system to improve the ease of cutter replacement; and
It is a further objective of the present invention to permit simple cutter replacement from the rear of the sheeting head without having to reach under the rollers and then guide the rotary cutter laterally through a side plate.
These and other objectives are met by a cutter replacement system that consists of a pair of guide rods located on the inner surfaces of the left and right hand side plates of the sheeting head. These rods are parallel and are oriented horizontally at right angles to the longitudinal axes of the rollers. The rotary cutter is held at either end by a cutter carriage that slidingly engages the guide rods. The cutter carriage is preferably equipped with a rotary cutter engagement system that moves a pivot arm and attached rotary cutter into an operational position in relation to the sheeting head. When the rotary cutter is to be serviced or replaced, the engagement system is released allowing the pivot arm to move the rotary cutter away from the front sheeting head roller, and cutter carriage holding the rotary cutter is slid rearward along the guide rods under the back roller so that it is readily accessible from a back side of the sheeting head.